The restaurant scenes were shot over the space of a week. By the end of the week, the smell of fish on set was so bad, it made people need to leave early.
This is Isabelle Huppert's second time playing a piano teacher in a psychological thriller, having also played one in the thriller The Piano Teacher (2001).
The original title of the film was "The Widow".
The distribution rights for the film were bought at the Toronto International Film Festival by Focus Features for $6 million.
The film is set in New York, but was actually filmed in Ireland.
Chloe Grace Moretz and Maika Monroe previously worked together on the YA film The 5th Wave (2016).
Greta's last name, "Hideg", is the Hungarian word for "cold".
In the film, Frances' friend's name is Erica. This is the same name as the character Isabelle Huppert plays in the 2001 psychosexual thriller, The Piano Teacher.
Neil Jordan spent 6 weeks in the gym in preparation to direct this film
Neil Jordan and Stephen Rea previously worked together in the 1992 film 'The Crying Game'.